Various studies have hitherto been made for the purpose of inhibiting photodegradation of agriculturally active ingredients which are unstable against light. There have been known technologies in which stabilizers such as an ultraviolet absorber are added (see, for example, Patent Document 1). There is also known a pesticidal composition in the form of an aqueous emulsion, which contains a specific water-soluble polymer as a stabilizer in an aqueous continuous phase (see, for example, Patent Document 2).